Mandrel with elastic sleeve utilizing hydraulic pressure for hydroforming hollow metal cylinders

ABSTRACT

A mandrel with an elastic sleeve utilizing hydraulic pressure for hydroforming hollow metal cylinders is disclosed. This invention simplifies the manufacturing process of the hydroforming device and reduces the associated cost, through the use of fluid pressures upon the elastic sleeve that biases forcefully against the interior of the metal cylinder being shaped. In the case where containment of the hydorforming fluid is desired, so as to prevent any contamination of the interior of the cylinder being shaped, this technology can provide that containment more reliably. The elastic sleeve material used is reasonably flexible, and more durable than other materials used in related devices.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional application upon the provisionalpatent application having Ser. No. 62/456,865 filed on Feb. 9, 2017.

FIELD OF INVENTION

This invention relates to the use of fluid pressures to radiallyhydroform a metal cylinder into the precise shape and dimensionsrequired for the finished product, including an elastic sleeve thatexpands against the interior of the cylinder to attain its preciserequired dimension.

BACKGROUND OF THE INVENTION

When using a fluid to radially hydroform a metal cylinder, it is oftendesirable to keep the fluid self-contained for various reasons includingbut not limited to contamination of the material to be formed, loss of avaluable fluid, or contamination of surrounding environment with saidfluid.

Other methods for hydroforming metal cylinders can be more expensive andcomplex to manufacture. Other methods for hydroforming may also notcontain the fluid used for the hydoforming process. Many forms ofapparatus used to hydroform metal cylinders rely on a soft material suchas an O-ring to be in intimate contact with the mandrel OD and thecylinder ID before, during and after hydroforming. This can lead toconsiderable resistance and require high amounts of force to insert andremove the apparatus. The O-rings are vulnerable to cuts and tearsduring the insertion process which leads to premature O-ring failure andinsufficient retention of the pressure required to hydroform the metalcylinder.

The inventor herein has obtained various prior United States patentsrelating to the technology of a System and Method for Radially ExpandingHollow Cylindrical Objects, such as can be seen in his U.S. Pat. No.9,468,966. He has also obtained U.S. Pat. No. 9,027,601, uponHydraulically Installed Tube Plug, Tube Plug Installation Tooling, andInstallation System and Method.

SUMMARY OF THE INVENTION

This invention contemplates the hydroforming of hollow metal cylinders,and attains such through the expansion of an elastic sleeve maintainedwithin the cylinder and subjected to substantial fluid compression forattaining the reshaping of the subject's cylinder from the use ofhydraulically stimulating pressures through the application of thesubject matter and mechanics of this invention.

The present embodiment accomplishes the above objectives. The apparatusutilizing an elastic sleeve does not rely on trapped fluid between themandrel OD and the cylinder ID to hydroform the cylinder. There are noO-rings or soft seal materials required to be in intimate contact withthe cylinder ID prior to introducing the fluid for the hydroformingprocess or after its completion. This eliminates the requirement forsoft seal material in the annular space between the apparatus and themetal cylinder that is to be hydroformed along with the issue of cutsand tears associated with such soft materials. This also eliminates thehigh forces that may be required to insert and remove the hydroformingapparatus.

It includes a hard metal mandrel shaft inside an elastic sleeve. Themandrel shaft shall provide a means of positioning and retaining theelastic sleeve in a precise location axially along the mandrel in itselfthus defining an expansion zone. Preferably this will be accomplishedwith a combination of bushings and locking nuts and manufactured from aninelastic material such as metal. The mandrel shaft shall have an axialpath in its center intersecting with a radial path that exits within theboundaries of the elastic sleeve. This path will be used as a means ofintroducing pressurized fluid into the annular space between the mandrelOD and the elastic sleeve ID. The mandrel shaft will have an annulargrooves located between the source of the pressurized fluid exiting themandrel shaft and prior to each end of the elastic sleeve. A softelastic material such as an O-ring shall reside in the annular groove toprovide a seal between the mandrel shaft OD and the elastic sleeve ID.

In the case where containment of the hydroforming fluid is desired, thistechnology can provide that containment more reliably. The elasticsleeve material used is more durable than other materials used insimilar devices, thus allowing more expansions, and reducing the amountof unproductive time spent replacing tooling parts. This embodimentsimplifies the manufacturing process of the hydoforming device andreduces the associated cost. Other features and advantages of theembodiment will become more apparent in the following drawings anddetailed description.

The object of this invention is to eliminate the need for soft materialseals between the expansion apparatus OD and the ID of the metalcylinder by radially hydroformed along with the concern for cuts andtears associated with the use of these seals. To reduce the operatorfatigue associated with inserting and removing an apparatus thatutilizes the soft seals previously discussed. To provide an apparatusthat contains the pressurized fluid during operation and returns itautomatically to its source when the pressure is reduced. To reduce thecost of manufacturing by simplifying the design of the apparatus andincrease the reliability.

Other objects and purposes for the subject matter of this invention mayoccur to those skilled in the art upon review of the disclosure asprovided herein. Such variations, if within the spirit of thisinvention, are intended to be encompassed within the scope of any claimsto patent protection issuing from this application.

BRIEF DESCRIPTION OF THE DRAWINGS

In referring to the drawings:

FIG. 1 is an exploded prospective view of a disassembled mandrelassembly;

FIG. 2 is a longitudinal cross section of a mandrel assembly positionedin a tube located in a tube sheet ready to begin expanding;

FIG. 3 is an enlarged longitudinal cross section of the overlappingmating surfaces of an elastic sleeve and a sleeve retaining bushing;

FIG. 4 is a longitudinal cross section of the overlapping matingsurfaces of an elastic sleeve and a sleeve retaining bushing describedin the second embodiment; and

FIG. 5. is a longitudinal cross section of the overlapping matingsurfaces of an elastic sleeve and a sleeve retaining bushing describedin the third embodiment.

VARIOUS COMPONENTS OF THE INVENTION

-   M. Mandrel Assembly-   1. Mandrel Shaft-   2. Reduced OD of Mandrel Shaft between Annular Grooves-   3. 3 a & 3 b—Threaded Sections-   4. 4 a & 4 b—Annular Grooves-   5. High Pressure Connector-   6. Recessed Section-   7. Polyurethane Back-up ring-   8. O-ring-   9. 9 a & 9 b—O-rings-   10. Elastic Sleeve-   11. Sleeve Retainer Bushing 11 a & 11 b-   12. Spacer washers 12 a & 12 b-   13. Nuts 13 a & 13 b-   14. Axial Passageway-   15. Radial Passageway-   17. Mandrel Adapter—Threaded-   20. Mandrel Assembly Sleeve retaining bushing-   21. Bushing Threads-   22. Locking nut-   23. Sleeve retaining bushing-   24. Sleeve internal threads

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Description of the FirstEmbodiment

Referring to FIG. 1 and FIG. 2, a mandrel assembly is made up of thefollowing components. The components are made of appropriate highstrength materials such as, but not limited to, steel, stainless steel,titanium, high strength metal alloys and plastic ceramics. An elasticsleeve, usually of a polymer, and made of polyurethane or similarmaterials with good machining and high elasticity properties. The choiceof materials can vary based on the application and environmentalrequirements that the assembly may be used in it.

A mandrel shaft 1 is made up of an appropriate high strength materialand is generally formed of a uniform diameter along its length where itjoins with reduced diameter threaded sections 3 a & 3 b, and a furtherreduced diameter high pressure connection 5 outboard of threaded section3 b. This allows components mounted thereon to be slid off and replacedwhen required. Annular grooves 4 a & 4 b are formed in the majordiameter section of the mandrel shaft 1. The mandrel shaft OD 2 betweenthe annular grooves 4 a & 4 b is of a reduced OD slightly less than themajor OD outboard of the grooves 4 a & 4 b. O-rings 9 a & 9 b which aremade of a suitably soft material as known in the art encircle themandrel shaft 1 and sit in the annular grooves 4 a & 4 b. The highpressure connection 5 is capable of joining the shaft to a variablepressure fluid supply up to 60,000 psi and has an annular recess 6formed in it. A polyurethane backup ring 7 and O-ring 8, which is madeof a suitably soft material, sits in the annular recess 6. The innerdiameters of backup 7 and O-ring 8 must be slightly smaller than theannular recess 6 diameter. The outer diameter of backup 7 must beslightly smaller than the major diameter of the high pressure connector5. The outer diameter of O-ring 8 must be slightly larger than the majordiameter of the high pressure connector 5. An elastic sleeve 10 made ofan appropriate material, as aforesaid, with good machining and elasticproperties with an ID slightly larger than the mandrel shaft 1 majordiameter allows it to slide in an axial direction on the mandrel shaft1. The elastic sleeve 10 major OD is equal to the sleeve retainerbushings 11 a & 11 b OD. Sleeve retainer bushings 11 a & 11 b are madeof an appropriate high strength material with an ID slightly larger thanthe OD of the mandrel shaft 1, has a major diameter to allow it to slidefreely in an axial direction on the mandrel shaft 1. The mating surfaces16 a & 16 b of the elastic sleeve 10 and sleeve retainer bushing 11 a &11 b that overrides and join with the elastic expander 10 surfaces arean interference fit. The elastic sleeve 10 and sleeve retainer bushing11 a & 11 b mating surfaces 16 a & 16 b can be an overlapping bevelsurface, an overlapping step surface, or overlapping interlocking matingsurfaces 16 a as depicted in FIG. 3.

Outboard and adjacent to the sleeve retainer bushings 11 a & 11 b areretaining washers 12 a & 12 b are made of an appropriate high strengthmaterial with an ID slightly larger than the OD of the threaded sections3 a & 3 b of the mandrel shaft 1, and an OD equal to the OD of thesleeve retainer bushings 11 a& 11 b. Outboard and adjacent to retainingwashers 12 a & 12 b are nuts 13 a & 13 b that are secured in threadedengagement with threaded sections 3 a & 3 b of the mandrel shaft 1 andlimits the axial movement of the components on the mandrel shaft 1locking them in place. The mandrel shaft 1 has an axial oriented centralbore 14 that intersects with a radially oriented bore 15 to provide apath for the pressurized fluid to reach the annular void between themandrel shaft 1 and the elastic sleeve 10. Various configurations ofhigh pressure adapters can be threaded onto the threaded end 3 b of themandrel to connect the mandrel shaft 1 to a high pressure fluid source.

The adapter 17, shown in FIG. 1 and FIG. 2, is shown as an example onlyand is not the sole means of connecting the mandrel shaft 1 to a highpressure fluid source. A high pressure flexible hose (not shown) may beattached directly to the mandrel assembly through an appropriatelythreaded mandrel adapter and used to supply pressurized fluid. Thisconfiguration allows for positioning the mandrel down a tube to apredetermined position from the tube end to hydroform the tube. Themandrel shaft 1 can be modified by continuing the axial passageway 14through the mandrel shaft 1 instead of stopping it mid-shaft, and a highpressure connection 5 added to the threaded section 3 a, may workappropriately at that end of the mandrel. This allows multiple mandrelassemblies of varying lengths to be interconnected end to end withinterconnections of varying lengths. When activated, multiple locationscan be hydroformed at similar or varying expansion lengths at the sametime. The mandrel shaft 1 can include a safety vent passageway thatallows the mandrel to be safely used to hydroform a hollow cylinder witha blind hole. The mandrel can be attached to a hand-held mandrel holderor a robotically controlled mandrel holder by changing the configurationof the mandrel adapter connections. An adjustable stop collar can beattached to the mandrel adapter by threads to facilitate fineadjustments in the mandrel insertion placement.

A technician would assemble the system as indicated above. The personwould then insert the mandrel assembly into the material to behydroformed. The person would actuate the power supply using either aremote operation switch on the mandrel holder handle or using a manualoperation switch located on the power supply. Pressurized fluid wouldthen be pumped from the power supply via a suitable umbilical capable ofdelivering the maximum rated output from the power supply's pump. Thepressurized fluid will enter the mandrel via passageways 14 & 15 andenter the annular void between mandrel shaft 1 and the elastic expander10. The pressurized fluid fills the void and exerts pressure radially onthe elastic expander 10. The elastic expander 10 deforms radiallyexerting pressure on the metal cylinder, expanding it radially. Theperson would hold the switch until the indicators would indicate thehydroforming process is complete. When the hydroforming process iscomplete, the person would release the switch and then remove themandrel assembly from the material.

Description of the Second Embodiment

Refer to FIG. 4. The sleeve retaining bushing 20 may have internalthreads 21 to engage external threads on the locking nut 22, therebycombining the sleeve retaining bushing, retaining washer, and lockingnut functions into one piece.

Description of the Third Embodiment

Refer to FIG. 5. The sleeve retaining bushing 23 used on the primary endof the mandrel (end nearest to the high pressure fluid source) may haveinternal threads 24 to match the threads on the mandrel shaft 1. It mayhave a major OD machined equal to or larger than the cylinder beingexpanded to facilitate precise positioning of the mandrel assembly, byindexing it off the end of the cylinder to be expanded. Therebycombining the sleeve retaining bushing, retaining washer, locking nut,and positioning collar functions into one piece.

Variations or modifications to the subject matter of this invention mayoccur to those skilled in the art upon review of the summary of theinvention as provided herein, and upon undertaking a study of thedescription of its preferred embodiment, in view of the drawings. Thesubject matter of this invention as explained, is set forth forillustrative purposes only.

I claim:
 1. An apparatus for radially expanding a cylinder byhydroforming the same utilizing hydraulic pressure, comprising: a metalcylinder to be expanded; a mandrel provided for insertion into saidmetal cylinder in preparation for performance of the hydroformingfunction; an elastic sleeve provided upon the mandrel at least along aportion of its length, and said elastic sleeve arranged in contiguitywith the interior of the cylinder to be hydroformed; said mandrel havingan internal approximate axial pathway through which hydraulic fluids mayinsert during hydroforming, said mandrel having at least one approximateradial pathway extending from its axial pathway to the surface of themandrel, and said pathways providing the means for introducing apressurized fluid to the area between the mandrel and its elastic sleeveto expand the elastic sleeve against the interior of the cylinder beinghydroformed interiorly thereof; seals provided between the elasticsleeve and the surface of the mandrel to seal in pressurized fluidduring hydroforming; said mandrel at one end having an adapter to whicha high pressure fluid source may connect therewith for introducingpressurized fluids into the mandrel in preparation for the performanceof hydroforming process upon the associated metal cylinder.
 2. Theapparatus of claim 1 and including a series of O-rings provided uponsaid mandrel and the interior of said elastic sleeve to contain thepressurized fluids therein during performance of a hydroformingfunction.
 3. The apparatus of claim 1, wherein said elastic sleeveslides onto said mandrel and contacts the O-rings operatively associatedwith said mandrel to form a hydraulic fluid pressure expansion zonebetween said elastic sleeve, and the exterior of said mandrel, to obtainexpansion of the elastic cylinder when hydroforming a metal cylinderinto an expanded shape.
 4. The apparatus of claim 3, wherein saidelastic sleeve extends over the substantial length of the said mandrelwhen assembled for a hydroforming operation.
 5. The apparatus of claim4, and including a bushing provided at each end of the elastic sleeve,and retaining washers and threaded nuts applied to each end of themandrel to hold the said bushings in place against the ends of theelastic sleeve to assure retention of the pressurized hydraulic fluidduring performance of a hydroforming operation.
 6. The apparatus ofclaim 5, and including a back up ring provided between the end of themandrel and within the adapter to maintain a seal of the pressurizedfluid as it enters into the mandrel during performance of a hydroformingfunction.
 7. The apparatus of claim 6, and including a further O-ringprovided to form the seal between the adapter and the proximate end ofthe mandrel to assure fluid sealing at that position.
 8. The apparatusof claim 1, wherein said elastic sleeve is formed of a polymer.
 9. Theapparatus of claim 8, said polymer is a polyurethane.